1. Field of the Invention
The present invention relates to a printer which prints on a print medium by a print command.
2. Description of the Prior Art
Printers can be is classified as impact printers which print by impacting a print paper by a hammer and non-impact printers which print without impacting the print paper. In any type of printer, it is very important to precisely fix a print head at a print position. An impact printer has a large impact force as compared to a non-impact printer such as a thermal printer and an ink jet printer, and hence it is necessary to rigidly fix the print head at a position displaced from a platen by a predetermined distance. A known impact printer has a daisy print wheel head which has types mounted at ends of a number of radial spokes and which is rotated at a high speed, and the printer actuates a print hammer when a selected type comes to a predetermined print position to impact the type to print a character on a print paper on a platen.
FIGS. 1 and 2 show an example of a daisy-type printer. Numeral 1 denotes a daisy-type wheel which is the heart of a print head and has types such as alphabetic and numeric characters mounted at ends of radially extending spokes. The type wheel is fixed to a rotary shaft 2 of a wheel motor (not shown) and is rotatable in both directions. Numeral 3 denotes a motor case having the wheel motor accommodated therein, and pins 4 and 5 are mounted on side surfaces thereof. Numeral 6 denotes a mounting frame fixed on a carriage, not shown, and grooves 7 for guiding the pins 4 and grooves 8 for guiding the pins 5 are formed on both side surfaces of the frame. A magnet device having a yoke 9 and a permanent magnet 10 is fixed to the bottom of the motor case 3 and attaches by an attraction force to a yoke 12 rotataby mounted to the mounting frame by a shaft 11 to fix the motor case 3 at a print position, that is, a position at which the type wheel 1 faces a platen, not shown.
In such a prior art printer, high precision is required for both contact surfaces of the permanent magnet 10 and the yokes 9 and contact surfaces of the yokes 9 and the yoke 12 in order to precisely fix the impact print head at the print position, and a fine adjustment is required to form one plane by end surfaces of the yokes 9 contacting to the yoke 12.